Superior Handgrip of Proficiency (3.5e Equipment)

From D&D Wiki

The Superior Handgrip of Proficiency is a flexible sheathe just right for a sword handle, but which can adjust shape to handle anything from a crossbow to even a small nub on the gripping surface of any non-ammunition weapon, just like it's lesser version. However, instead of granting proficiency in a single particular weapon for 1 minute, as per its spell Master's Touch, it instead grants proficiency in the single weapon's type, and constantly, for a higher price. Thus you could hold a sai in one hand with the handgrip, and still be proficient in the sai in your other hand without a second handgrip.

Removing or adding a handgrip is a move action which provokes attacks of opportunity.